Pass C# ASP.NET array to Javascript array

Question

Does anyone know how to pass a C# ASP.NET array to a Javascript array? Sample code will also be nice.

Sorry if I was vague earlier guys. The question is actually quite simple. Let's say for simplicity that in my aspx.cs file I declare:

int [] numbers = new int[5];

now I want to pass "numbers" to the client side and use the data in the array within javascript. How would I do this?

Answer 1

serialize it with System.Web.Script.Serialization.JavaScriptSerializer class and assign to javascript var

dummy sample:

<% var serializer = new System.Web.Script.Serialization.JavaScriptSerializer(); %>
var jsVariable = <%= serializer.Serialize(array) %>;

Answer 2

In the page file:

<script type="text/javascript">
    var a = eval('[<% =string.Join(", ", numbers) %>]');
</script>

while in code behind:

public int[] numbers = WhatEverGetTheArray();

Answer 3

You can use ClientScript.RegisterStartUpScript to inject javascript into the page on Page_Load.

Here's a link to MSDN reference: http://msdn.microsoft.com/en-us/library/asz8zsxy.aspx

Here's the code in Page_Load:

  List<string> tempString = new List<string>();
  tempString.Add("Hello");
  tempString.Add("World");

  StringBuilder sb = new StringBuilder();
  sb.Append("<script>");
  sb.Append("var testArray = new Array;");
  foreach(string str in tempString)
  {
    sb.Append("testArray.push('" + str + "');");
  }
  sb.Append("</script>");

  ClientScript.RegisterStartupScript(this.GetType(), "TestArrayScript", sb.ToString());

Notes: Use StringBuilder to build the script string as it will probably be long.

And here's the Javascript that checks for the injected array "testArray" before you can work with it:

if (testArray)
{
  // do something with testArray
}

There's 2 problems here:

1. Some consider this intrusive for C# to inject Javascript

2. We'll have to declare the array at a global context

If you can't live with that, another way would be to have the C# code save the Array into View State, then have the JavaScript use PageMethods (or web services) to call back to the server to get that View State object as an array. But I think that may be overkill for something like this.

Answer 4

This is to supplement zerkms's answer.

To pass data across language barriers, you would need a way to represent the data as a string by serializing the data. One of the serialization methods for JavaScript is JSON. In zerkms's example, the code would be placed inside of an aspx page. To combine his example and yours together on one aspx page, you would have,

<%
    int[] numbers = new int[5];
    // Fill up numbers...

    var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
%>

somewhere later on the aspx page

<script type="text/javascript">
    var jsVariable = <%= serializer.Serialize(numbers) %>;
</script>

This answer though, assumes that you are generating JavaScript from the initial page load. As per the comments in your post, this could have been done via AJAX. In that case, you would have the server respond with the result of the serialization and then deserialize it in JavaScript using your favorite framework.

Note: Also do not mark this as an answer since I wanted the syntax highlighting to make another answer more clear.